Electric machine, insulating cap and method for forming an insulating cap

ABSTRACT

The electric machine has a stator with windings connected to phase connections. An insulating cap protects the reciprocally connected portions of the phase connections and windings. The insulating cap has a box-shaped body with an opening for the introduction of a winding within it. The body defines a seat housing the phase connection. The seat is formed in one piece with the body.

RELATED APPLICATION

This application claims priority under 35 U.S.C. §119 to EuropeanApplication No. 10461533.1, filed 9 Nov. 2010, the entirety of which isincorporated by reference herein.

FIELD OF INVENTION

The present disclosure relates to an electric machine, an insulating capand a method for forming an insulating cap.

BACKGROUND

FIG. 1 shows a traditional connection between windings 2 of a stator ofan electric machine such as a generator and phase connections 4 (phaserings).

This connection typically comprises a conductive element 3 brazed at oneside to the winding 2 and at the other side to the phase connection 4.

Above the winding 2 end, conductive element 3 and phase connections 4end an insulating cap 5 is provided to insulate and protect thecomponents housed therein.

As shown, traditional caps 5 are made is two elements; a first element 6that houses the winding 2 end and the greatest part of the conductiveelement 3, and a second element 7 that envelopes the phase connection 4end and has its ends that overlap the borders of the first element 6 atzones 8.

Putty 9 is also provided within the first and second elements 6, 7 tomechanically fix the cap 5 and electrically insulate the componentshoused therein.

These caps 5 proved to be very efficient and provide an excellentinsulation, but in some cases, their use could be troubling.

In fact, the minimum distance between two adjacent caps 5 must be largeenough to avoid discharges (this is the so called electric distance thatdepends on the materials, voltage, etc).

With the described traditional caps the minimum distance is much smallerthan what possible, because of overlapping of the second parts 7 on thefirst parts 6 of the caps 5. This causes large constrains in the machinedesign (for example with reference to the number of slots housing thewindings) or maximum voltage achievable.

In addition, an upgrade of a machine such as an electric generator (byincreasing the operating voltage) would not be possible, because theupgraded voltage would be too high for the actual distances betweenadjacent caps 5.

Moreover, assembling of the two pieces 6, 7 of the caps 5 and at thesame time the application of putty is typically very time consuming.

SUMMARY

The present disclosure is directed to an electric machine including astator; a plurality of windings provided on the stator and a phaseconnection. The phase connection providing at least a portion of anelectrical connection between at least two of the plurality of windings.The electric machine also including an insulating cap that electricallyinsulates an interconnection of said phase connection and a respectiveone of the at least two windings. The insulating cap has a body portionand a seat, the body portion has an opening that receives a portion ofthe respective one winding. The seat receives a portion of the phaseconnection, and is integral with said body portion.

In another aspect, the disclosure is directed to an insulating cap for arotating electric machine. The insulating cap includes a body portionhaving an opening configured to receive a portion of a winding of therotating electric machine; and a seat. The body portion has a firstlongitudinal side wall, a second longitudinal side wall opposite thefirst side wall, a third side wall that extends from the first side wallto the second side wall, and an upper wall that extends laterally fromthe first side wall to the second side wall and that extendslongitudinally from the third side wall to the seat. The seat isintegrally formed with the body portion and the seat is U-shaped,opening in a direction away from the body portion.

In a further aspect, the disclosure is directed to a method formanufacturing an insulating cap for a rotating electric machine. Themethod includes removing at least a portion of a first wall of abox-like body so as to define a first open surface that delimits thebody. The method also includes removing at least a second portion of asecond wall of said body that is adjacent to said first open surface soas to define a second open surface that is adjacent to said first opensurface and delimits said body.

The disclosure, in a further aspect, is also directed to an electricmachine having a stator with windings connected to phase connections. Aninsulating cap protecting reciprocally connected portions of the phaseconnections and windings is provided. The insulating cap having abox-shaped body with an opening for the introduction of a winding withinit. The body defines a seat housing the phase connection, and the seatis formed in one piece with the body.

The present disclosure is, in another further aspect, directed to aninsulating cap for a rotating electric machine having a box-shaped bodywith at least one opening. The body defines a seat that is formed in onepiece with the body, and the seat is U-shaped having side walls whichface away from the body.

In a still further aspect, the disclosure is directed to a method forforming an insulating cap for a rotating electric machine. The methodincludes, cutting a box-shaped body and removing at least a portion of afirst wall and defining a first open surface delimiting the body. Themethod also includes cutting at least a second portion of a second wallthat is adjacent to the first open surface to define a second opensurface adjacent to the first open surface and delimiting the body.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages will be more apparent from thedescription of a preferred but non-exclusive embodiment of the machine,cap and method illustrated by way of non-limiting example in theaccompanying drawings, in which:

FIG. 1 is a top view of traditional caps;

FIGS. 2 and 3 respectively show a perspective view and a top view ofcaps in an embodiment of the disclosure;

FIGS. 4 and 5 show respectively a bottom view and a cross sectionthrough line V-V of FIG. 4 of a cap in an embodiment of the disclosure;in these figures the cap ready to be installed on an electric machine isdepicted in solid line and portions of the cap to be cut and removedbefore it is assembled on the electric machine are depicted in dashedline;

FIG. 6 schematically shows a top view of the caps wrapped with a tape;and

FIG. 7 schematically shows a portion of an electric machine such as anelectric generator.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Introduction To theEmbodiments

One of numerous aspects is to provide a machine, a cap and a methodallowing an increased distance between adjacent caps, in order toachieve more design flexibility (for example in the number of slots orin the voltage) or improved upgrade possibilities.

Another aspect is to provide a machine, a cap and a method, which permitquicker assembly.

These and further aspects are attained by providing a machine, a cap anda method in accordance with the accompanying claims.

Advantageously, the cap is very robust (more than traditional caps),which allows a simpler wedging between the caps than with traditionalcaps.

DETAILED DESCRIPTION

In FIGS. 1 through 7 like reference numerals designate identical orcorresponding parts throughout the several views.

The electric machine has a stator 10 with windings 2 and a rotor 11. Thewindings 2 are connected to phase connections 4 via the conductiveelements 3.

With particular reference to FIGS. 2 and 3, an insulating cap 5protecting the reciprocally connected portions of the phase connections4 and windings 2 is provided.

In particular, reference 5 a designates the cap provided to insulate theconnection between an upper winding within a slot and a phase connection4; likewise, 5 b designates the cap provided to insulate the connectionbetween a bottom winding within the slot and a phase connection 4.

Each insulating cap 5 has a box-shaped body 15 with an opening 16 forthe introduction of a winding 2 within it.

In addition, the body 15 defines a seat 17 housing the phase connection4; this seat 17 is formed in one piece with the body 15.

In particular, the seat 15 is U-shaped, with the side walls 19 of theU-shaped seat 15 facing away from the body 15.

The seat 17 and the cap 15 are filled with putty 9.

Advantageously, between the winding 2 and the phase connection 4, aconductive element 3 is provided that is fully housed within the cap 5.

In FIGS. 2 and 3, the caps 18 covering, protecting and insulating thereciprocally connected ends of the windings are also shown.

With reference to FIGS. 4 and 5, before it is mounted on the electricmachine, the cap 5 has the body 15 with the seat 17 closed by walls 22,23 depicted in dashed lines.

This structure is used to test the electrical properties of the cap; itis clear that since only one part must be tested for each cap (insteadof two like with traditional caps) these tests are quicker.

Then the walls 22 and 23 are cut to form the seat 17 and the caps 5 aremounted by filling them with putty 9 and placed above the winding 2 end,conductive element 3 and phase connection 4 end. It is clear that sinceonly one element must be cut and mounted, assembling is also quickerthan with traditional caps.

In addition, as clearly shown in FIG. 3, since the caps have nooverlapping zones causing thicker portions, also the minimum distance issensibly increased, allowing design flexibility, voltage increase andmore upgrade possibilities.

Tapes 24 a, 24 b can be provided; these tapes can be wrapped in thecircumferential direction (arrows 24 a) and in axial direction (arrows24 b). When provided, these tapes do not substantially alter thedistance between adjacent caps 5 (i.e. they are very thin).

The present disclosure also relates to a method for forming aninsulating cap 5 for a rotating electric machine comprising the steps ofcutting a box-shaped body 15 and removing at least a portion of a firstwall 22 to define a first open surface 25 delimiting the body 15.

Advantageously, also at least a second portion of a second wall 23 thatis adjacent to the first open surface 25 is cut, to define a second opensurface 26 adjacent to the first open surface 25 and delimiting the body15; the open surfaces 25, 26 allow a U-shaped seat 17 to be defined.

Naturally the features described may be independently provided from oneanother.

In practice the materials used and the dimensions can be chosen at willaccording to requirements and to the state of the art.

REFERENCE NUMBERS

2 winding

3 conductive element

4 phase connection

5, 5 a, 5 b insulating cap

6 first element of 5

7 second element of 5

8 zone of 5

9 putty

10 stator

11 rotor

15 body

16 opening

17 seat

18 cap

19 walls of 17

22 wall of 15 to be removed

23 wall of 15 to be removed

24 a, 24 b tape

25 open surface of 15

26 open surface of 15

1. An electric machine, comprising: a stator; a plurality of windingsprovided on said stator; a phase connection, said phase connectionproviding at least a portion of an electrical connection between atleast two of said plurality of windings; and an insulating cap thatelectrically insulates an interconnection of said phase connection and arespective one of said at least two windings, wherein said insulatingcap has a body portion and a seat, said body portion having an openingthat receives a portion of said respective one winding, said seatreceiving a portion of said phase connection, said seat being integralwith said body portion.
 2. The electric machine of claim 1, wherein saidbody portion has a first side wall that extends from said respective onewinding to said phase connection, a second side wall that extends fromsaid respective one winding to said phase connection, a third side wallthat extends from said first side wall to said second side wall, and anupper wall that extends laterally from said first side wall to saidsecond side wall and that extends longitudinally from said third sidewall to said seat.
 3. The electric machine of claim 2, wherein said seatcomprises a wall portion that extends substantially perpendicular tosaid upper wall in a direction away from said body portion.
 4. Theelectric machine of claim 1, wherein said seat is U-shaped, saidU-shaped seat opening in a direction away from said body portion.
 5. Theelectric machine of claim 4, wherein an entire volume of said seat thatis not occupied by said phase connection is filled with putty.
 6. Theelectric machine of claim 1, wherein an entire volume of said insulatingcap that is not occupied by said phase connection, said respective onewinding and said interconnection is filled with putty.
 7. The electricmachine of claim 1, wherein said interconnection is a conductiveelement.
 8. The electric machine of claim 5, wherein an entirety of saidconductive element is located within said insulating cap.
 9. Aninsulating cap for a rotating electric machine, said insulating capcomprising: a body portion having an opening configured to receive aportion of a winding of said rotating electric machine; and a seat,wherein said body portion has a first longitudinal side wall, a secondlongitudinal side wall opposite said first side wall, a third side wallthat extends from said first side wall to said second side wall, and anupper wall that extends laterally from said first side wall to saidsecond side wall and that extends longitudinally from said third sidewall to said seat, said seat is integrally formed with said body portionand said seat is U-shaped, which opens in a direction away from saidbody portion.
 10. The insulating cap of claim 9, wherein said seatcomprises a wall portion that extends substantially perpendicular tosaid upper wall in a direction away from said body portion.
 11. A methodfor manufacturing an insulating cap for a rotating electric machine,said method comprising: removing at least a portion of a first wall of abox-like body so as to define a first open surface that delimits thebody, removing at least a second portion of a second wall of said bodythat is adjacent to said first open surface so as to define a secondopen surface that is adjacent to said first open surface and delimitssaid body.
 12. Electric machine having a stator with windings connectedto phase connections, wherein an insulating cap protecting reciprocallyconnected portions of the phase connections and windings is provided,the insulating cap having a box-shaped body with an opening for theintroduction of a winding within it, wherein the body defines a seathousing the phase connection, and the seat is formed in one piece withthe body.
 13. Electric machine according to claim 12, wherein the seatis U-shaped, and wherein side walls of the U-shaped seat face away fromthe body.
 14. Electric machine according to claim 13, wherein the seatis filled with putty.
 15. Electric machine according to claim 13,wherein the cap is filled with putty.
 16. Electric machine according toclaim 13, further comprising a conductive element arranged between thewinding and the phase connection.
 17. Electric machine according toclaim 16, wherein the conductive element is fully housed within the cap.18. Insulating cap for a rotating electric machine having a box-shapedbody with at least one opening, wherein the body defines a seat that isformed in one piece with the body, and the seat is U-shaped having sidewalls which face away from the body.
 19. Method for forming aninsulating cap for a rotating electric machine, the method comprising:cutting a box-shaped body and removing at least a portion of a firstwall and defining a first open surface delimiting the body, and cuttingat least a second portion of a second wall that is adjacent to the firstopen surface to define a second open surface adjacent to the first opensurface and delimiting the body.